Additive for stabilizing water-containing fuels and a fuel stabilized with this additive

ABSTRACT

The invention relates to an additive for stabilizing a water-containing liquid hydrocarbon fuel, which comprises an alcohol of 5-10 carbon atoms, 0.5-3 parts by weight, calculated for 1 part by weight of said alcohol, of a carboxylic amide of 5-10 carbon atoms, and 3-10 parts by weight, calculated for 1 part by weight of said alcohol, of a carboxylic acid of 5-10 carbon atoms. The invention also relates to a stabilized liquid fuel for an internal combustion engine, which comprises 10-40% by weight of water, 45-85% by weight of a liquid hydrocarbon fuel, and 5-15% by weight of an additive as defined above, all percentages being calculated for the total weight of said liquid fuel.

FIELD OF THE INVENTION

The invention relates to an additive which can be used with good resultsto stabilize liquid fuels which, beside liquid hydrocarbons (such aspetrol, gasoline, diesel fuel, kerosine) utilised as fuels for internalcombustion engines, also contain water. The invention also relates tofuels stabilized with said additive, as well as to a process forpreparing thereof. The invention also relates to the use of saidadditives to stabilize water-containing liquid hydrocarbon fuels, aswell as to the use of such stabilized fuels to operate internalcombustion engines.

BACKGROUND OF THE INVENTION

It is known that the performance of internal combustion engines can beincreased by adding water to the liquid organic fuel. The amount ofliquid organic fuel required to operate the engine can also be reducedby adding water to it. A favourable consequence of the above is that theoctane number of gasoline can be increased by adding water to it, and,as a second favourable consequence, environmental damages resulting fromthe combustion of organic fuels can be suppressed.

Although since about 60 years efforts have been taken to exploit theabove advantages as full as possible, by the solutions known before itcould be done only on the expense of very high investments, whichsometimes have not been in proportion to the attained results. Thus, forexample, during the second world war—in order to increase theperformance—such a technical solution was applied for Focker typefighters where water was injected into the cylinders of the engine by aseparate injector after the electric ignition. Indeed, this solutionresulted in a 10-15% increase in performance, however, to operate theengines, it was required to modify their structure and to install anexactly adjusted injector. With aircrafts it was a considerable furtherdisadvantage that mounting of the injector and of a separate water tankresulted in an undesired increase in weight.

According to the method disclosed in EP 0 177 484 A1 a dispersion offuel and water has been injected into the combustion chamber of theengine. For this end considerable technical modifications had to beperformed on the structure of the engine, and various additionalstructural elements (such as heat exchanger, collector, etc.) had alsoto be installed. The solution disclosed in EP 0 142 580 A1 is based onthe same principle; it differs from the previous one essentially only inthe structural modifications performed on the engine.

According to the method disclosed in EP 0 311 877 A2 water has beenintroduced into the combustion chamber as steam rather than as adispersion formed with the fuel. This requires the use of a specificcylinder head, and several accessories hadd also to be installed to theengine.

Thus, the solutions listed above have the common disadvantage that boththe engine and its technical surroundings should be modifiedconsiderably which, on one hand, runs with high costs, and, on the otherhand, the thus-modified structure cannot be operated with a conventionalfuel any more. Structural modifications were required primarily becausethe aqueous fuel could not be stabilized for a sufficiently prolongedperiod of time which would enable a safe operation, thus one had to formthe water/fuel mixture directly in the combustion chamber from itscomponents. These solutions did not attain a widespread practical use,just because of the specific structural requirements discussed above.

U.S. Pat. No. 5 156 114 discloses the use of liquid fuels containing20-80 v/v % of water in internal combustion engines. This solution alsorequires a modification of the engine in such a way that ahydrogen-evolving catalyst should be placed into the combustion chamber,generally as the electrically negative pole of the ignition. Thishydrogen-evolving catalyst converts at least part of the water,introduced together with the organic fuel, into hydrogen and oxygen, andthe evolved hydrogen is combusted together with the organic fuel. Theresulting power surplus, together with the power surplus resulting fromsteam expansion, fully compensates for the power loss which arises fromlowering the amount of the organic fuel.

This patent discusses primarily the use of aqueous methanol or aqueousethanol as fuel, where inhomogenity problems do not emerge, since bothof the organic components are fully miscible with water. In one of theexamples the author also refers to the use of aqueous diesel fuel, andremarks here that the fuel mix should be used as an emulsion, andadditional bypipes should be fit to the engine in order to avoidundesirable water condensation. No data can be found in this paper onthe stability of the emulsion comprising water and organic hydrocarbonfuel; and only a very general information is given on the applicablesurfactants, saying that all of the commercially available substanceswhich assist hydrocarbon fuels to be dispersed in water fit for thispurpose.

One of the disadvantages of the solution disclosed in the cited paper isthat the engine (and, when hydrocarbon fuels are used, its accessories,too) should still be modified, although these modifications are no moredisturbing when the engine is operated with hydrocarbon fuel alone. As amuch more serious disadvantage, the engine can be operated either with afully water-miscible fuel type (i.e. with alcohol or aqueous alcohol) orwith a water-immiscible fuel type (i.e. with a hydrocarbon or with anemulsion of water and hydrocarbon), because any eventual mixing of thetwo fuel types immediately causes stability problems and operationaldisturbances associated therewith. Thus when the fuel type actuallyfilled into the tank is not available at the refuelling station, eitherthe content of the tank should be consumed completely before changingthe fuel type, or the vehicle should be equipped with two separate fueltanks. Of course, such stability problems may also arise when thehydrocarbon-based fuels already present in the tank and to be topped uphave different water contents. As a serious insufficiency, the citedpaper does not give any actual solution on the stabilization ofwater-containing liquid hydrocarbon fuels. Thus, despite of itsadvantages, the solution disclosed in the cited patent has not becomewidespread with internal combustion engines operated with liquidhydrocarbons.

In our previous international patent application No. PCT/HU97/00029 wehave disclosed a method for stabilizing aqueous mixtures of liquidhydrocarbon fuels with various surfactants or surfactant mixtures. By aproper selection of the emuls-fying agents and combinations thereof wesucceeded to form aqueous liquid hydrocarbon fuel compositions whichwere stable for a relatively prolonged period of time and which could bedirectly combusted in all types of the widely used internal combustionengines, without requiring the engine to be modified or additionalaccessories to be installed. In this way all of the favourableconsequences of water introduction (increase in power, savings inhydrocarbons, increase in octane number, etc.) can be well exploitedwithout modifying the structures of the existing engines.

Upon a more accurate evaluation of the demands it appeared, however,that, with regard to the requirements of operational safety,transporting and storage, only those water-containing liquid hydrocarbonfuels can find commercial utility which, in addition to providing allthe advantages attributable to the presence of water, are fully clear,transparent and free of sediments, retain this state for several years,and are relatively insensitive to being mixed with a fuel of other watercontent (“topping up”). The compositions disclosed in the cited patentapplication do not fully satisfy these increased requirements.

Continuing our research work we have found, unexpectedly, that aqueousliquid hydrocarbon fuels which fully meet the above requirements can beobtained when they are stabilized with an additive comprising

an alcohol of 5-10 carbon atoms,

0.5-3 parts by weight, calculated for 1 part by weight of said alcohol,of a carboxylic amide of 5-10 carbon atoms, and

3-10 parts by weight, calculated for 1 part by weight of said alcohol,of a carboxylic acid of 5-10 carbon atoms.

Thus, in one aspect, the invention relates to an additive of the abovecomposition.

DETAILED DESCRIPTION OF THE INVENTION

The additive according to the invention differs from the compositionssuggested before to stabilize aqueous liquid hydrocarbon fuels basicallyin that none of its components is a surfactant. It is extremelysurprising that when this additive is mixed with water and a liquidhydrocarbon fuel a fully clear, transparent liquid is obtained, whichretains its stability for several years (the oldest ones of the samplestested till the priority date did not change after a storage of 3years). It has also been found that when the additive according to theinvention is added to a mixture of a liquid hydrocarbon fuel and water,a slight warming occurs upon mixing. This phenomenon does not occur whenthe additive is mixed only with water or only with liquid hydrocarbonfuel, even more, sometimes a limited water-miscibility is observed.Although we do not intend to bound our invention to theoreticalconsiderations, on the basis of the above we assume that in the jointpresence of water and liquid hydrocarbon fuel the individual componentsof the additive react with one another and/or with water and/or with theliquid hydrocarbon in a hitherto non-elucidated way, and, as a result ofthis(these) chemical reaction(s), a continuous phase transition on analmost molecular level occurs between the initially immiscible aqueousand oily components.

The carbon backbone of the alcohols, carboxylic amides and carboxylicacids present in the additive according to the invention may bestraight-chained, branched or cyclic, and may optionally containunsaturated bonds, but aromatic structures are excluded. The alcoholsmay be monohydric and polyhydric ones, of which the polyhydric alcohols(polyols) are preferred. Similarly, the carboxylic acids may also bemono- or polycarboxylic acids, of which the latter ones are preferred.The carboxylic amides may be amides derived from mono- or polycarboxylicacids, including those compounds which are partially amidated on thecarboxy groups.

The alcohol, carboxylic amide and carboxylic acid components may beeither single compounds or they may be mixtures of two or more alcohols,carboxylic amides or carboxylic acids, respectively.

If desired, one or more conventional fuel additives may also be admixedwith the additive according to the invention. Such conventional fueladditives are e.g. cetane number increasing agents, combustionaccelerators, wear improving agents and corrosion inhibitors. Thesesubstances can be added to the additive according to the invention inthe usual amounts defined by their purposes, which is well known to oneskilled in the art.

In a further aspect, the invention relates to a stabilized liquid fuelfor internal combustion engines, which comprises, calculated for thetotal weight of the fuel,

10-40 (preferably 15-35) % by weight of water,

45-85 (preferably 50-70) % by weight of a liquid hydrocarbon fuel, and

5-15 (preferably 10-15) % by weight of a stabilizing additive as definedabove.

The stabilized liquid fuel according to the invention may comprisepreferably tap water, with no regard of its hardness, however,demineralized water and distilled water can also be used.

The liquid hydrocarbon fuel component of the stabilized fuel accordingto the invention may be any of the liquid hydrocarbon cutsconventionally used to operate an internal combustion engine, of whichpetrol, gasoline, diesel fuel and kerosine are mentioned. The stabilizedliquid fuel according to the invention may also comprise, beside theadditive according to the invention, one or more other conventionaladditives, such as cetane number increasing agents, corrosioninhibitors, etc., which may be present in their conventional amounts.These other additives are also included in the term and amount of liquidhydrocarbon fuel, thus the term “liquid hydrocarbon fuel” also coversliquid hydrocarbon fuels comprising one or more conventionaladditive(s). Here we remark that when the liquid hydrocarbon is petrol,it is not required to add an octane number increasing additive to thestabilized liquid fuel according to the invention, since the waterpresent exerts a considerable octane number increasing effect. This is avery important advantage of the petrol-based fuel stabilized accordingto the invention.

When the liquid hydrocarbon component of the aqueous fuel to bestabilized is one of the first (light) cuts of mineral oil distillation,it is generally preferred to use an additive where the individualcomponents contain up to 7 carbon atoms.

The stabilized liquid fuel according to the invention is prepared bymixing the components with one another. As it is a very simpleoperation, it can be performed at the place of storage or even justbefore the use of the fuel. Although the order of introducing thecomponents to be mixed with one another is not too critical, due to itssimplicity it proved to be preferable to add the additive according tothe invention, as a preformed mix, to a preformed mix of water andliquid hydrocarbon fuel. The optionally required further additives, ifthey are not already present in the additive and/or in the liquidhydrocarbon fuel, can be introduced in any step. However, the componentscan be admixed in a different order. Even more, the individualcomponents of the additive according to the invention can be admixedseparately with the fuel components, although it is a more laboursomeand less advantageous solution.

In a further aspect, the invention relates to the use of an additiveaccording to the invention for stabilizing a water-containing liquidhydrocarbon fuel. The invention also relates to the use of a stabilizedfuel according to the invention to operate an internal combustionengine.

In our operation tests we have found that the stabilized fuel accordingto the invention can be admixed (“topped up”) with another fuel withoutany decrease in power or any other observable change in the operation ofthe engine, provided that the liquid hydrocarbon present in the twofuels is of the same type. This is a very important advantage withrespect of refueling. Thus the stabilizing additive according to theinvention has the additional advantage that it can well balance theeventual quality differences between fuels obtainable at differentrefuelling stations, and it enables one to admix the stabilized fuelaccording to the invention with a conventional (water-free) fuel withoutany hitch.

A further advantage of the additive according to the invention is that,when the engine is operated, all of its components are fully combustedwithout providing harmful substances, and no harmful substances areexhausted to the environment from the additive. In our operation testsengines operated with the stabilized fuel according to the inventionwere tested for their emissions, and exhaust gases were analysed fortheir compositions. The parameters important from the aspects ofenvironment protection (NO, NO_(x), CO, CO₂) were always found to bemuch more favourable than those observed with engines operated with thesame liquid hydrocarbon fuel containing no water and no additiveaccording to the invention. With diesel fuel operated engines aconsiderable decrease in smoke emission was observed.

Further details of the invention are presented in the followingnon-limiting Examples.

EXAMPLES

This example presents the preparation of a fuel applicable for apetrol-operated, four-stroke engine equipped with an injector and with acatalyst. The experiences obtained on a trial run, and the quality testresults of the fuel are also given.

A Mazda 626 type passenger car equipped with a 2.2 liter injector engineof 12 valves, which had run before 318,000 km, was used as test vehicle.The fuel according to the invention was prepared from 658 g of unleadedpetrol with an octane number of 91, 70 g of additive (composed of 0.7part by weight of pentane carboxamide, 0.7 part by weight ofcyclohexanol and 5.6 parts by weight of pentanedicarboxylic acid) and272 g of tap water with a German degree of hardness of 23° in such a waythat the additive was added to the water under continuous stirring, andthe resulting mixture was added to the unleaded petrol under continuousstirring. Thereafter the mixture was homogenized in an electric mixeruntil a fully transparent fuel was obtained. The resulting fuel wasfilled into the previously emptied tank of the petrol-operated vehicle.After starting, the speed of the vehicle was increased in the usual wayto 80 km/hour, and the car was driven with an approximately constantspeed until the fuel run out. In this test the accelerating ability ofthe engine was the same as before, and no running irregularity ormisfire was observed. Under these conditions a drive of 18.2 km could betaken. When repeating the test under the same conditions but using 1 kgof unleaded petrol with an octane number of 91, a drive of 15.5 km couldbe taken. No colour change of the spark plugs could be observed.

In the second stage of the test the consequences of the change-oversfrom the fuel according to the invention to normal fuel and from normalfuel to the fuel according to the invention were examined. Change-overswere performed by simply topping up the tank. No observable change inthe operation of the engine could be found in either of thechange-overs.

The additive disclosed in this example is applicable, upon appropriatelyincreasing its amount, up to a petrol:water weight ratio of 60:40.

The quality test results of the fuel according to the invention, havingthe composition as disclosed in this Example, are listed in Table 1below. For comparison purposes, the results observed with unleaded,water-free petrol with an octane number of 91 are also given.

Example 1

Unleaded normal Fuel according petrol (octane Property to the inventionnumber: 91) Water content, % (MSZ 11745:1980) 27.2 0 Octane numbertheoretical (MSZ 11708:1980) 79.5 94.5 motoric (MSZ 11706:1980) 116.784.0 Lead content, g/l (MSZ 10874:1979) 0.001 0.002 Corrosion effect oncopper plate l.a. l.a. (MSZ 11788:1979A) (MSZ = Hungarian Standard)

Results of power tests performed on a test bench are given in Table 2.In these test the standard power was adjusted to 225 VA. 200 ml of fuelwere used in each of the tests. The tests were performed with fuelsobtained by admixing unleaded petrol (octane number: 91), the additiveof the composition as given in Example 1, and water in an amount asindicated in Table 2.

TABLE 2 Petro +5% +10% +15% +20% +25% (ON 91) water water water waterwater Time unit, sec 537 570 615 658 715 770 Power, % 100 106.1 121.0126.3 127.5 143.3

Example 2

The test vehicle was a diesel fuel operated VW microbus with an engineof 1.5 l cylinder capacity and having no turbocharger, which had runbefore 48.000 km. The water-containing fuel was prepared as follows: 50g of an additive (composed of 1.5 parts by weight ofpentane-carboxamide, 0.5 part by weight of octanol and 3 parts by weightof decanedicarboxylic acid/C₁₀H₁₈O₄/) were added to 250 g of tap water,and the resulting aqueous mixture was added, under intense stirring, to700 g of diesel fuel. Stirring was continued until a fully transparentliquid was obtained. Thereafter the trial run described in Example 1 wasrepeated. A drive of 17.0 km could be taken until the fuel run out,whereas when neat diesel fuel was used, only a drive of 16.0 km could betaken under otherwise the same conditions. No anomalies in operationcould be observed upon change-over from the fuel according to theinvention to normal diesel fuel and vice versa. The additive disclosedin this example is applicable, upon appropriately increasing its amount,up to a diesel fuel: water weight ratio of 60:40.

In a further test performed with the fuel disclosed in this Example, anIkarusz 256 bus with a nominal engine power of 190 HP was used as testvehicle. The prescribed fuel consumption of the vehicle was 29.0liters/100 km. Before starting the use of the fuel according to theinvention, the vehicle was subjected to motor diagnostic tests, theresults of which were as follows:

a) Compression final pressure:

Cylinder 1: 22 bars

Cylinder 2: 20 bars

Cylinder 3: 24 bars

Cylinder 4: 20 bars

Cylinder 5: 23 bars

Cylinder 6: 24 bars (average: 22.166 bars)

b) Opening pressure of the injectors: 190 bars

c) Specific fuel consumption in 3 months before the test:

first month: 26.67 liters/100 km

second month: 24.74 liters/100 km

third month: 27.13 liters/100 km

average for the 3 months: 26.18 liters/100 km

d) Lubricating oil consumption: 0.0 liter

The summarized motor diagnostic test results gave the followingqualification: the compression final pressure is only acceptable, as thedeviations are rather high; both fuel consumption and lubricating oilconsumption are excellent.

Thereafter the vehicle was operated continuously with the fuel disclosedin Example 2, and after a run of 8042 km the diagnostic tests wererepeated. The following results were obtained:

a) Compression final pressure:

Cylinder 1: 22 bars

Cylinder 2: 23 bars

Cylinder 3: 23 bars

Cylinder 4: 23 bars

Cylinder 5: 23 bars

Cylinder 6: 22 bars (average: 22.66 bars)

b) Opening pressure of the injectors:

Cylinder 1: 190 bars

Cylinder 2: 195 bars

Cylinder 3: 195 bars

Cylinder 4: 195 bars

Cylinder 5: 180 bars

Cylinder 6: 185 bars

c) Specific fuel consumption during the test period: 27.01 liters/100 km

d) Lubricating oil consumption: none

The summarized motor diagnostic test results gave the followingqualification: although there is a slight increase in the compressionfinal pressure of the cylinders, the overall pressure shows a fullyuniform pattern, thus the result is excellent. Although there is anegligible increase in specific fuel consumption (3.1%), it stillremains significantly below the prescribed value (93.13%).

We claim:
 1. An additive composition for stabilizing a water-containingliquid hydrocarbon fuel, which comprises: an alcohol of 5 to 10 carbonatoms; 0.5 to 3 parts by weight, calculated for 1 part by weight of saidalcohol, of a carboxylic amide of 5 to 10 carbon atoms; and 3 to 10parts by weight, calculated for 1 part by weight of said alcohol, of acarboxylic acid of 5 to 10 carbon atoms.
 2. An additive as claimed inclaim 1 for stabilizing a water-containing light mineral oil cut fuel,in which the alcohol, carboxylic acid amide and carboxylic acidcomponents each comprise up to 7 carbon atoms.
 3. A stabilized liquidfuel for an internal combustion engine, which comprises: 10 to 40% byweight of water; 45 to 85% by weight of a liquid hydrocarbon fuel; and 5to 15% by weight of an additive as claimed in claim 1, wherein the abovepercentages are calculated for the total weight of said stabilizedliquid fuel.
 4. A stabilized liquid fuel as claimed in claim 3, whereinsaid liquid hydrocarbon fuel is a light mineral oil cut fuel, andwherein the alcohol, carboxylic acid amide and carboxylic acidcomponents of said additive each comprise up to 7 carbon atoms.
 5. Astabilized liquid fuel as claimed in claim 3, which comprises 15% to 35%by weight of water, calculated for the total weight of said stabilizedliquid fuel.
 6. A stabilized liquid fuel as claimed in claim 3, whichcomprises 50% to 70% by weight of said liquid hydrocarbon fuel,calculated for the total weight of said stabilized liquid fuel.
 7. Astabilized liquid fuel as claimed in claim 3, which comprises 10% to 15%by weight of said additive, calculated for the total weight of saidstabilized liquid fuel.
 8. A method for stabilizing a water-containingliquid hydrocarbon fuel comprising adding to said water-containing fuelan additive of claim 1 or 2, or a liquid hydrocarbon fuel comprisingsaid additive.
 9. A stabilized liquid fuel as claimed in claim 4, whichcomprises 15% to 35% by weight of said water, calculated for the totalweight of said stabilized liquid fuel.
 10. A stabilized liquid fuel asclaimed in claim 4, which comprises 50% to 70% by weight of said liquidhydrocarbon fuel, calculated for the total weight of said stabilizedliquid fuel.
 11. A stabilized liquid fuel as claimed in claim 4, whichcomprises 10% to 15% by weight of said additive, calculated for thetotal weight of said stabilized liquid fuel.
 12. A stabilized liquidfuel as claimed in claim 5, which comprises 50% to 70% by weight of saidliquid hydrocarbon fuel, calculated for the total weight of saidstabilized liquid fuel.
 13. A stabilized liquid fuel as claimed in claim9, which comprises 50% to 70% by weight of said liquid hydrocarbon fuel,calculated for the total weight of said stabilized liquid fuel.
 14. Astabilized liquid fuel as claimed in claim 5, which comprises 10% to 15%by weight of said additive, calculated for the total weight of saidstabilized liquid fuel.
 15. A stabilized liquid fuel as claimed in claim6, which comprises 10% to 15% by weight of said additive, calculated forthe total weight of said stabilized liquid fuel.
 16. A stabilized liquidfuel as claimed in claim 9, which comprises 10% to 15% by weight of saidadditive, calculated for the total weight of said stabilized liquidfuel.
 17. A stabilized liquid fuel as claimed in claim 10, whichcomprises 10% to 15% by weight of said additive, calculated for thetotal weight of said stabilized liquid fuel.
 18. A stabilized liquidfuel for an internal combustion engine, which comprises: 10%to 40% byweight of water; 45%to 85% by weight of a liquid hydrocarbon fuel; and5%to 15% by weight of an additive, wherein all percentages arecalculated for the total weight of said stabilized liquid fuel, andwherein said additive is selected from the additive of claim 1 or claim2.
 19. A process for preparing a stabilized liquid fuel of claim 18,which comprises mixing together said water, said liquid hydrocarbon fueland said additive, or the individual components thereof, to form saidstabilized fuel.
 20. A liquid hydrocarbon fuel comprising the additiveof claim 1 or claim 2.